Hi Jean-Paul, Another question which might be the reason why I am getting the inconsistencies in my newton-raphson convergence. I just realised this..
What I am doing is the following - I am giving small compressive displacements to the film+substrate. I am also calculating the eigenvalues of the tangent_stiffness matrix (after the convergence of newton method), to understand the stability of the system. The moment I encounter a negative smallest eigenvalue, I want to go to a previous time step and would like to solve for a small compressive displacement. For instance, if the compression is 0.1 at this time step and the eigenvalue is negative, I go to the previous time step and give a compressive displacement of 0.05. Here is my concern, I have added a condition that, if I find a negative eigenvalue during any time step, I update the *solution_n = solution_n - solution_delta*; and then run the time step again (with a smaller compressive displacement) after doing *solution_delta = 0.0*. Since the next state is also dependent on the updated quadrature point data (stresses etc.), I would also need to update the quadrature point data to the previous step. Could you please let me know, how am I supposed to do that? In the documentation in code gallery <https://dealii.org/developer/doxygen/deal.II/code_gallery_Quasi_static_Finite_strain_Compressible_Elasticity.html>, it is written that - "*The first function is used to create a material object and to initialize all tensors correctly: The second one updates the stored values and stresses based on the current deformation measure **Grad**u**n*" (inside the Point History class). However, I only find one function which is setup_lqp, and not the update_lqp or something similar. Thanks! Animesh On Tuesday, November 10, 2020 at 5:24:13 PM UTC+5:30 Animesh Rastogi IIT Gandhinagar wrote: > Hi Jean-Paul, > > There seem to be some inconsistencies in the simulations results that I am > getting, therefore I wanted to check if I have applied the material laws > properly accounting for the heterogeneities. Below, I have addted the > edited functions that are responsible for that. Could you please let me > know if there is something wrong here? I have checked the material > properties (mu1, mu2 etc), and they are being read correctly by the code > from the parameters file. I have also checked that the material ids (1 and > 2) are correctly applied to the cells where I need them. > > -------------------------------------- > void setup_lqp (const Parameters::AllParameters ¶meters, const > unsigned int &materialid) > { > > //Material 1 - Thin Film > if (materialid == 1) > { > > std::cout<<"1_id"<<std::endl<<parameters.mu1<<std::endl<<parameters.nu1<<std::endl; > material.reset(new > Material_Compressible_Neo_Hook_One_Field<dim,NumberType>(parameters.mu1, > parameters.nu1)); > } > //Material 2 - Substrate > if (materialid ==2) > { > material.reset(new > Material_Compressible_Neo_Hook_One_Field<dim,NumberType>(parameters.mu2, > parameters.nu2)); > } > > } > > ------------------------------------------- > > template <int dim,typename NumberType> > void Solid<dim,NumberType>::setup_qph() > { > std::cout << " Setting up quadrature point data..." << std::endl; > > quadrature_point_history.initialize(triangulation.begin_active(), > triangulation.end(), > n_q_points); > > for (typename Triangulation<dim>::active_cell_iterator cell = > triangulation.begin_active(); cell != triangulation.end(); > ++cell) > { > const std::vector<std::shared_ptr<PointHistory<dim,NumberType> > > > lqph = > quadrature_point_history.get_data(cell); > Assert(lqph.size() == n_q_points, ExcInternalError()); > > for (unsigned int q_point = 0; q_point < n_q_points; ++q_point) > lqph[q_point]->setup_lqp(parameters, cell->material_id()); > } > } > > -------------------------------------- > > Thanks! > > Animesh > On Tuesday, November 3, 2020 at 12:09:03 PM UTC+5:30 Animesh Rastogi IIT > Gandhinagar wrote: > >> Hi Jean, >> >> Sorry for late response. Thank you for your detailed answer. Using your >> suggestions I was able to assign the material ids to different area of my >> domain of interest. >> >> Thanks again! >> >> Animesh >> >> On Tuesday, October 27, 2020 at 3:05:39 AM UTC+5:30 Jean-Paul Pelteret >> wrote: >> >>> Dear Animesh, >>> >>> Let me preface my suggestion by saying that you can introduce some >>> heterogeneity in more than one way. That is, you're not bound to using a >>> material ID (which is what I'm going to suggest), but you could use some >>> geometric arguments to determine which class or material properties should >>> dictate the constitutive response at a continuum point. You also need not >>> use the class-based structure that this code galley example has. There are >>> other tutorials (e.g. step-8) that use Functions that return the material >>> coefficients at any point in space. So you should keep that in mind as you >>> read my suggestion. >>> >>> In my opinion, the simplest approach would be the following: >>> >>> 1. The PointHistory::setup_lqp() function >>> <https://github.com/dealii/code-gallery/blob/master/Quasi_static_Finite_strain_Compressible_Elasticity/cook_membrane.cc#L720-L724> >>> >>> is the point at which the constitutive law at some quadrature point is set. >>> So you should extend this function in some way to make a decision about >>> which material it is in, and what the material law at that point is. The >>> first thing that you might do is add an argument for the material ID, and >>> then choose constiutitve parameters based on the material ID. You'll note >>> that the concrete constitutive law is stored in a pointer. This makes it >>> easy to extend to support other constitutive laws, because you can for >>> example abstract the Material_Compressible_Neo_Hook_One_Field class into >>> some base class and other classes (maybe a >>> Material_Compressible_Mooney_Rivlin_One_Field) and then, based on the >>> material ID, select which constitutive law is applied at that quadrature >>> point. >>> 2. The PointHistory::setup_lqp() function is called from >>> Solid::setup_qph() >>> <https://github.com/dealii/code-gallery/blob/master/Quasi_static_Finite_strain_Compressible_Elasticity/cook_membrane.cc#L1203-L1211> >>> >>> , and more specifically inside a loop over all cells. Its possible to >>> retrieve the cell->material_id() or cell->center() (or, if you create a >>> quadrature rule to help you then you can get the actual position of the >>> quadrature point if you want such granularity). You can then pass this >>> information in to PointHistory::setup_lqp() to help decide which >>> constitutive law / parameters to apply. If using the material ID then you >>> will, of course, want to set the material ID when building or reading in >>> your triangulation. >>> >>> That is, at least, how I typically do things when using this code as a >>> basis for extension. I hope that this helps you introduce heterogeneities >>> into your problem! >>> >>> Best, >>> Jean-Paul >>> >>> >>> On 26.10.20 08:15, Animesh Rastogi IIT Gandhinagar wrote: >>> >>> Hello All, >>> >>> I am trying to solve the wrinkling problem of a thin stiff film attached >>> to a soft substrate in dealii. I am using the code - from the code gallery >>> for this purpose. For the simulations, I would have to consider the film >>> and the substrate with different material properties. >>> >>> I understand that I would have to do something within the class >>> Qudrature point history. However, I am getting a little confused on how to >>> approach it. It would be great if someone could help me with this. >>> >>> This is the code that I am using for this purpose - >>> https://dealii.org/developer/doxygen/deal.II/code_gallery_Quasi_static_Finite_strain_Compressible_Elasticity.html >>> >>> Thanks! >>> >>> Animesh >>> >>> -- >>> The deal.II project is located at http://www.dealii.org/ >>> For mailing list/forum options, see >>> https://groups.google.com/d/forum/dealii?hl=en >>> --- >>> You received this message because you are subscribed to the Google >>> Groups "deal.II User Group" group. >>> To unsubscribe from this group and stop receiving emails from it, send >>> an email to dealii+un...@googlegroups.com. >>> To view this discussion on the web visit >>> https://groups.google.com/d/msgid/dealii/26db8831-e190-4fcd-8247-b7172ab880fen%40googlegroups.com >>> >>> <https://groups.google.com/d/msgid/dealii/26db8831-e190-4fcd-8247-b7172ab880fen%40googlegroups.com?utm_medium=email&utm_source=footer> >>> . >>> >>> >>> -- The deal.II project is located at http://www.dealii.org/ For mailing list/forum options, see https://groups.google.com/d/forum/dealii?hl=en --- You received this message because you are subscribed to the Google Groups "deal.II User Group" group. To unsubscribe from this group and stop receiving emails from it, send an email to dealii+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/dealii/f1209ac5-a4b8-46d4-84f3-12ca38f7d8f2n%40googlegroups.com.
